Methods of forming trench isolation regions

ABSTRACT

The invention includes methods of forming trench isolation regions. In one implementation, a masking material is formed over a semiconductor substrate. The masking material comprises at least one of tungsten, titanium nitride and amorphous carbon. An opening is formed through the masking material and into the semiconductor substrate effective to form an isolation trench within semiconductive material of the semiconductor substrate. A trench isolation material is formed within the isolation trench and over the masking material outside of the trench effective to overfill the isolation trench. The trench isolation material is polished at least to an outermost surface of the at least one of tungsten, titanium nitride and amorphous carbon of the masking material. The at least one of tungsten, titanium nitride and amorphous carbon is/are etched from the substrate. Other implementations and aspects are contemplated.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. patentapplication Ser. No. 10/817,029, now U.S. Pat. No. 7,015,113, filed Apr.1, 2004, entitled “Methods of Forming Trench Isolation Regions”, namingGaro J. Derderian and H. Montgomery Manning as inventors, the disclosureof which is incorporated by reference.

TECHNICAL FIELD

This invention relates to methods of forming trench isolation regions.

BACKGROUND OF THE INVENTION

In typical semiconductor device applications, numerous devices arepacked into a small area of a semiconductor substrate to create anintegrated circuit. Many of the individual devices are electricallyisolated from one another. Accordingly, electrical isolation is anintegral part of semiconductor device design for preventing unwantedelectrical coupling between adjacent components and devices.

Conventional methods of isolating circuit components typically usetrench isolation regions. Such are formed by depositing or otherwiseforming a masking layer over a semiconductor substrate. Trenches areetched through the masking layer into the semiconductor substrate, withthe trenches being subsequently filled with insulative material.Exemplary masking materials for trench isolation include silicon nitrideand polysilicon with or without an underlying pad oxide layer. Furtherafter forming the trenches, they are typically lined with siliconnitride which ultimately forms part of the trench isolation material.Sidewalls of the trenches are typically oxidized as well to form silicondioxide and either before or after the nitride liner deposition.

The trench isolation material which is formed in the isolation trenchestypically includes deposition of insulative material over the maskingmaterial and to within the trenches, typically over-filling them. Theisolation material is typically then polished back, for example bychemical-mechanical polishing, at least to the outer surface of themasking material. The masking material is then typically selectivelyetched away from the substrate leaving, at least at this point in theprocess, insulative isolation material filling and extending outwardlyof the trench isolation regions. Unfortunately where the maskingmaterial comprises silicon nitride and where silicon nitride is alsoutilized to line the trenches, the nitride liner might get etched aswell. This can cause nitride liner recessing within the trenchesrelative to the outer surface of the semiconductive material of thesubstrate. This can result in gate oxide wrap-around that can degradethe transistors which are ultimately fabricated.

While the invention was motivated in addressing the above identifiedissues, it is in no way so limited. The invention is only limited by theaccompanying claims as literally worded, without interpretative or otherlimiting reference to the specification, and in accordance with thedoctrine of equivalents.

SUMMARY

The invention includes methods of forming trench isolation regions. Inone implementation, a masking material is formed over a semiconductorsubstrate. The masking material comprises at least one of tungsten,titanium nitride and amorphous carbon. An opening is formed through themasking material and into the semiconductor substrate effective to forman isolation trench within semiconductive material of the semiconductorsubstrate. A trench isolation material is formed within the isolationtrench and over the masking material outside of the trench effective tooverfill the isolation trench. The trench isolation material is polishedat least to an outermost surface of the at least one of tungsten,titanium nitride and amorphous carbon of the masking material. The atleast one of tungsten, titanium nitride and amorphous carbon is/areetched from the substrate.

In one implementation, a method of forming a trench isolation regioncomprises forming masking material over a semiconductor substrate, whereat least some of the masking material is oxidizable. An opening isformed through the masking material and into the semiconductor substrateeffective to form an isolation trench within semiconductive material ofthe semiconductor substrate. The opening and the isolation trench haverespective sidewalls. The substrate is exposed to oxidizing conditionseffective to oxidize the masking material sidewalls at a greater ratethan which the sidewalls of the semiconductive material are oxidized.Trench isolation material is formed within the isolation trench.

In one implementation, a method of forming a trench isolation regioncomprises forming a masking material over a semiconductor substrate. Anopening is formed through the masking material and into thesemiconductor substrate effective to form an isolation trench withinsemiconductive material of the semiconductor substrate. A siliconnitride comprising layer is deposited within the isolation trench andover the masking material effective to line the trench. Trench isolationmaterial is deposited over the silicon nitride comprising layer withinthe isolation trench and over the masking material outside of thetrench. The trench isolation material and the silicon nitride comprisinglayer are polished at least to the masking material. The maskingmaterial and the trench isolation material are removed relative to thesilicon nitride comprising layer from outwardly of semiconductivematerial of the semiconductor substrate effective to leave a portion ofthe silicon nitride comprising layer projecting outwardly fromsemiconductive material of the semiconductor substrate.

Other implementations and aspects are contemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic section view of a semiconductor wafer fragmentin process in accordance with an aspect of the invention.

FIG. 2 is a view of the FIG. 1 wafer fragment at a processing subsequentto that depicted by FIG. 1.

FIG. 3 is a view of the FIG. 2 wafer fragment at a processing subsequentto that depicted by FIG. 2.

FIG. 4 is a view of the FIG. 3 wafer fragment at a processing subsequentto that depicted by FIG. 3.

FIG. 5 is a view of the FIG. 4 wafer fragment at a processing subsequentto that depicted by FIG. 4.

FIG. 6 is a diagrammatic section view of another semiconductor waferfragment in process in accordance with an aspect of the invention.

FIG. 7 is a diagrammatic section view of another semiconductor waferfragment in process in accordance with an aspect of the invention.

FIG. 8 is a view of the FIG. 7 wafer fragment at a processing subsequentto that depicted by FIG. 7.

FIG. 9 is a view of the FIG. 8 wafer fragment at a processing subsequentto that depicted by FIG. 8.

FIG. 10 is a diagrammatic section view of another semiconductor waferfragment in process in accordance with an aspect of the invention.

FIG. 11 is a view of the FIG. 10 wafer fragment at a processingsubsequent to that depicted by FIG. 10.

FIG. 12 is a view of the FIG. 11 wafer fragment at a processingsubsequent to that depicted by FIG. 11.

FIG. 13 is a view of the FIG. 12 wafer fragment at a processingsubsequent to that depicted by FIG. 12.

FIG. 14 is a diagrammatic section view of another semiconductor waferfragment in process in accordance with an aspect of the invention.

FIG. 15 is a view of the FIG. 14 wafer fragment at a processingsubsequent to that depicted by FIG. 14.

FIG. 16 is a diagrammatic section view of another semiconductor waferfragment in process in accordance with an aspect of the invention.

FIG. 17 is a view of the FIG. 16 wafer fragment at a processingsubsequent to that depicted by FIG. 16.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

An exemplary embodiment method of forming a trench isolation region isinitially described with reference to FIGS. 1-5. FIG. 1 depicts asemiconductor substrate 10 comprising bulk semiconductive material 12,for example monocrystalline silicon. Although the invention is describedthroughout in the preferred context of bulk semiconductor processing,semiconductor-on-insulator fabrication methods as well as any othermethods of fabricating trench isolation regions are contemplated inaccordance with the invention. In the context of this document, the term“semiconductor substrate” or “semiconductive substrate” is defined tomean any construction comprising semiconductive material, including, butnot limited to, bulk semiconductive materials such as a semiconductivewafer (either alone or in assemblies comprising other materialsthereon), and semiconductive material layers (either alone or inassemblies comprising other materials). The term “substrate” refers toany supporting structure, including, but not limited to, thesemiconductive substrates described above. Further in the context ofthis document, the term “layer” encompasses both the singular and theplural.

A masking material 14 is formed over and comprises semiconductorsubstrate 10. In the depicted exemplary embodiment, such comprises a padoxide layer 16 and a layer 18 formed thereover. An exemplary thicknessfor layer 16 is from 20 Angstroms to 75 Angstroms, with 60 Angstromsbeing a preferred specific example. Masking material layer 18 preferablyhas a thickness of from 200 Angstroms to 1,500 Angstroms, with 500Angstroms being a specific preferred example. Masking material layer 18comprises at least one of tungsten (in elemental and/or alloy form),titanium nitride and amorphous carbon. In one embodiment where amorphouscarbon is utilized, it might comprise at least one of boron andnitrogen.

Further in one exemplary embodiment with respect to amorphous carbon,such might comprise a layer that is transparent to visible light. In thecontext of this document, an amorphous carbon comprising layer that istransparent to visible light means that the amorphous carbon comprisinglayer has a substantially low absorption coefficient (k) in which k hasa range between about 0.15 and about 0.001 (or lower) at wavelength 633nm. The amorphous carbon comprising layer transparent to visible lightrange radiation, by way of example only, might be formed at atemperature from about 200° C. to about 450° C., with an exemplarypreferred pressure range being from about 3 Torr to about 7 Torr. Aspecific preferred example is 375° C. and 5 Torr. Such depositionpreferably occurs by plasma generation, with an exemplary power appliedto the showerhead being from 500 watts to 1100 watts, with 800 wattsbeing a specific preferred example. An exemplary flow rate for the C₃H₆is from 400 sccm to 2400 sccm, with 1450 sccm being a specific preferredexample. An exemplary preferred flow rate for the helium is from 250sccm to 650 sccm, with 450 sccm being a specific preferred example. Anexemplary preferred spacing of the showerhead/substratesupport-susceptor is 240 mils. Exemplary additional or other hydrocarbongases utilizable in producing transparency as described include CH₄,C₂H₂, C₂H₄, C₂H₆, and C₃H₈. A preferred gas provided during suchdeposition might be either one gas or a combination of various gases,including the absence of any helium. Further, lower temperaturedepositions can result in greater transparency than higher temperaturedepositions. By way of example only, an exemplary deposition thicknessover the substrate for the amorphous carbon comprising layer is 4000Angstroms. If boron and/or nitrogen doping of the amorphous carboncomprising layer is desired, an exemplary boron source gas is B₂H₆ at anexemplary flow rate of 1500 sccm, and an exemplary nitrogen source gasis N₂ at an exemplary flow rate of 1000 sccm. Where boron doping isdesired, an exemplary concentration range in the layer for boron is from0.5% atomic to 60% atomic. Where nitrogen doping is desired, anexemplary concentration range in the layer for nitrogen is from 0.1%atomic to 20% atomic.

Hard masking and/or antireflective coating layers might be utilized overmasking material layer 18. In one preferred embodiment, masking material14 is void of silicon nitride.

Referring to FIG. 2, an opening 20 has been formed through maskingmaterial 14 into semiconductor substrate 10 effective to form anisolation trench 22 within semiconductive material 12 of semiconductorsubstrate 10. An exemplary preferred manner of doing so is byphotolithographic patterning, development and etching, whether usingexisting or yet-to-be developed technologies.

Referring to FIG. 3, trench isolation material 24 has been formed withinisolation trench 22 and over masking material 14 outside of trench 22effective to overfill isolation trench 22. An exemplary preferredmaterial is silicon dioxide, for example high density plasma depositedsilicon dioxide, and further, for example, with or without thermal oxideand/or silicon nitride trench liner materials.

Referring to FIG. 4, trench isolation material 24 has been polished atleast to an outermost surface of the at least one of tungsten, tungstennitride and amorphous carbon material 18 of masking material 14.Exemplary preferred techniques include chemical-mechanical polishing,for example utilizing any existing or yet-to-be developed CMP tool andslurries.

Referring to FIG. 5, the at least one of tungsten, titanium nitride andamorphous carbon material 18 has been etched from the substrate.Preferably, the etching is conducted selectively to at least some oftrench isolation material 24, with the etching as shown being selectiveto all of trench isolation material 24. In the context of this document,a selective etch or removal removes one material compared to another ata ratio of at least 2:1. The exemplary pad oxide layer 16 might also beremoved, as well as some or all of material 24 from outwardly ofisolation trench 22.

By way of example only, an alternate exemplary embodiment to thatdepicted by FIG. 4 is illustrated in FIG. 6 in connection with asemiconductor substrate 10 a. Like numerals from the first-describedembodiment are utilized where appropriate, with differences beingindicated with different numerals or with the suffix “a”. Maskingmaterial 14 a comprises at least two of tungsten, titanium nitride andamorphous carbon with, for example, an outer layer 19 of at least one ofsuch materials being received outwardly of masking material layer 18 awhich comprises another of at least one of tungsten, titanium nitrideand amorphous carbon. In one exemplary embodiment, material 19preferably comprises amorphous carbon and material 18 a comprises atleast one of tungsten and tungsten nitride.

By way of example only, another exemplary embodiment method of forming atrench isolation region is described with reference to FIGS. 7-9 inconnection with a semiconductor substrate 10 b. Like numerals from thefirst-described embodiment are utilized where appropriate, withdifferences being indicated with different numerals or with the suffix“b”. Referring to FIG. 7, trench isolation material 24 b has been formedwithin isolation trench 22 and over masking material 14 outside oftrench 22 effective to overfill isolation trench 22. Trench isolationmaterial 24 b includes a silicon nitride comprising layer 30 and atleast one material 32 other than silicon nitride formed thereover. Anexemplary thickness for layer 30 is 70 Angstroms, and an exemplarypreferred material for layer 32 is high density plasma deposited silicondioxide. Of course, a thermal silicon dioxide layer might be formed ontrench sidewalls 22 before or after deposition of layer 30.

Referring to FIG. 8, trench isolation material 24 b has been polished toat least an outermost surface of the at least one of tungsten, titaniumnitride and amorphous carbon material 18 of masking material 14.

Referring to FIG. 9, the at least one of tungsten, titanium nitride andamorphous carbon material 18 has been etched from the substratesubstantially selectively to silicon nitride comprising layer 30. By wayof example only, an exemplary etching chemistry for etching elementaltungsten, amorphous carbon, and/or TiN selectively relative to siliconnitride comprises H₂SO₄ and H₂O₂ at a 9:1 ratio by weight at 140° C.Further by way of example only, an exemplary etching chemistry foretching elemental tungsten and/or TiN selectively relative to siliconnitride comprises H₂O, HCl, and H₂O₂ at a 20:4:1 ratio by weight at 70°C.

Yet another exemplary method of forming a trench isolation region isdescribed in connection with FIGS. 10-13 in connection with asemiconductor substrate 10 c. Like numerals from the first-describedembodiment are utilized where appropriate, with differences beingindicated with different numerals or with the suffix “c”. Referringinitially to FIG. 10, a masking material 14 c has been formed oversemiconductor substrate 12. Such is depicted as comprising a pad oxidelayer 16 and an overlying material 18 c, at least some of which isoxidizable. Thicknesses are preferably as described above in connectionwith the first described embodiment. Exemplary materials include thoseas described above, specifically tungsten, amorphous carbon, and/ortungsten nitride. An additional alternate exemplary material ispolysilicon, whether updoped or doped with another material or materialssuch as boron and/or phosphorus. Additional oxidizable masking materialsare contemplated, whether existing or yet-to-be developed. Regardless,in one exemplary preferred embodiment, masking material 14 c is void ofsilicon nitride.

Referring to FIG. 10, an opening 20 is formed through masking material14 c and into semiconductor substrate 10 c effective to form anisolation trench 22 within semiconductive material 12 of semiconductorsubstrate 10 c. Mask opening 20 has sidewalls 34, and isolation trench22 has sidewalls 36.

Referring to FIG. 11, substrate 10 c has been exposed to oxidizingconditions effective to oxidize masking material sidewalls 34 at agreater rate than that at which sidewalls 36 of semiconductor material12 are oxidized. Thereby in one preferred embodiment, an oxide layer 39is formed which is laterally thicker over the masking material sidewallswithin opening 20 than over the sidewalls of semiconductive material 12.

Referring to FIG. 12, trench isolation material 24 c has been formedwithin isolation trench 22. Such might comprise one or more materials,with material 39 also comprising trench isolation material. Processingmight otherwise continue as described above in connection with thefirst-described embodiments, for example whereby materials 24 c, 39 and14 c are removed outwardly from semiconductive material 12, for exampleas shown in FIG. 13.

An alternate exemplary embodiment semiconductor substrate 10 d isdepicted in FIGS. 14 and 15. Like numerals from the FIGS. 10-13embodiment are utilized where appropriate, with differences beingindicated with different numerals or with the suffix “d”. Referring toFIG. 14, semiconductor substrate 10 d is shown as being formed tocomprise trench isolation material 24 d comprising a silicon nitridecomprising layer 42 received over (and “on”, as shown) the oxidizedmasking material sidewalls and oxidized semiconductive materialsidewalls (i.e., on material 39). An exemplary additional material 44 isformed thereover, for example high density plasma deposited silicondioxide.

Referring to FIG. 15, and by way of example only, subsequent processingis depicted whereby all material has been removed outwardly frommaterial 12 of semiconductor substrate 10 d.

Yet another preferred method of forming a trench isolation region inaccordance with aspects of the invention is described in connection witha semiconductor substrate 10 e in FIGS. 16 and 17. Like numerals fromthe first-described embodiments are utilized where appropriate, withdifferences being indicated with different numerals or with the suffix“e”. Referring to FIG. 16, a masking material 14 is formed over asemiconductor substrate 12. Any material is contemplated, and includingfor example those described above, and preferably with such maskingmaterial being void of silicon nitride. An opening 20 has been formedthrough masking material 14 and into semiconductor material 12 effectiveto form an isolation trench 22 within material 12 of semiconductorsubstrate 10 e. A silicon nitride comprising layer 50 has been depositedwithin isolation trench 22 and over masking material 14 effective toline trench 22. An exemplary thickness for layer 50 is from 10 Angstromsto 150 Angstroms. Trench isolation material 24 has been deposited oversilicon nitride comprising layer 50 within isolation trench 22 and overmasking material 14 outside of trench 22. Exemplary preferred materialsare as described above, namely high density plasma deposited silicondioxide. FIG. 16 depicts such trench isolation material 24 and siliconnitride comprising layer 50 as having been polished at least to maskingmaterial 14.

Referring to FIG. 17, masking material 14 and trench isolation material24 have been removed relative to silicon nitride comprising layer 50from outwardly of semiconductive material 12 of semiconductive substrate10 e effective to leave a portion of silicon nitride comprising layer 50projecting outwardly of semiconductive material 12 of semiconductivesubstrate 10 e. An exemplary technique for such processing, where forexample material 24 is silicon dioxide and material 18 is polysiliconincludes dipping or spraying with a 25:1 by volume solution of H₂O:HF atroom temperature and pressure conditions. Alternately with polysiliconand silicon dioxide, such a solution could be utilized initially tostrip any native oxide overlying material 18 followed by etchingpolysilicon with tetramethyl ammonium hydroxide (TMAH). An exemplarysuch solution is 2.25% TMAH by weight in deionized water at 30° C.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method of forming a trench isolation region comprising: forming amasking material over a semiconductor substrate; the masking materialcomprising at least one of tungsten, titanium nitride and amorphouscarbon; forming an opening through the masking material and into thesemiconductor substrate effective to form an isolation trench withinsemiconductive material of the semiconductor substrate; forming trenchisolation material within the isolation trench and over the maskingmaterial outside of the trench effective to overfill the isolationtrench, the trench isolation material comprising a siliconnitride-comprising layer having at least one material other than siliconnitride formed thereover; polishing the trench isolation material atleast to an outermost surface of the at least one of tungsten, titaniumnitride and amorphous carbon of the masking material; and after thepolishing, etching the at least one of tungsten, titanium nitride andamorphous carbon from the substrate substantially selectively to thesilicon nitride-comprising layer and etching all remaining of themasking material from the substrate.
 2. The method of claim 1 whereinthe masking material comprises tungsten.
 3. A method of forming a trenchisolation region comprising: forming a masking material over asemiconductor substrate; the masking material comprising titaniumnitride; forming an opening through the masking material and into thesemiconductor substrate effective to form an isolation trench withinsemiconductive material of the semiconductor substrate; forming trenchisolation material within the isolation trench and over the maskingmaterial outside of the trench effective to overfill the isolationtrench, the trench isolation material comprising a siliconnitride-comprising layer having at least one material other than siliconnitride formed thereover; polishing the trench isolation material atleast to an outermost surface of the titanium nitride of the maskingmaterial; and etching the titanium nitride of the masking material fromthe substrate substantially selectively to the siliconnitride-comprising layer.
 4. The method of claim 1 wherein the maskingmaterial comprises amorphous carbon.
 5. A method of forming a trenchisolation region comprising: forming a masking material over asemiconductor substrate; the masking material comprising amorphouscarbon comprising at least one of boron and nitrogen; forming an openingthrough the masking material and into the semiconductor substrateeffective to form an isolation trench within semiconductive material ofthe semiconductor substrate; forming trench isolation material withinthe isolation trench and over the masking material outside of the trencheffective to overfill the isolation trench, the trench isolationmaterial comprising a silicon nitride-comprising layer having at leastone material other than silicon nitride formed thereover; polishing thetrench isolation material at least to an outermost surface of theamorphous carbon of the masking material; and etching the amorphouscarbon of the masking material from the substrate substantiallyselectively to the silicon nitride-comprising layer.
 6. The method ofclaim 5 wherein the amorphous carbon comprises both boron and nitrogen.7. A method of forming a trench isolation region comprising: forming amasking material over a semiconductor substrate; the masking materialcomprising amorphous carbon which is transparent to visible light;forming an opening through the masking material and into thesemiconductor substrate effective to form an isolation trench withinsemiconductive material of the semiconductor substrate; forming trenchisolation material within the isolation trench and over the maskingmaterial outside of the trench effective to overfill the isolationtrench, the trench isolation material comprising a siliconnitride-comprising layer having at least one material other than siliconnitride formed thereover; polishing the trench isolation material atleast to an outermost surface of the amorphous carbon of the maskingmaterial; and etching the amorphous carbon of the masking material fromthe substrate substantially selectively to the siliconnitride-comprising layer.
 8. A method of forming a trench isolationregion comprising: forming a masking material over a semiconductorsubstrate; the masking material comprising at least two of tungsten,titanium nitride and amorphous carbon; forming an opening through themasking material and into the semiconductor substrate effective to forman isolation trench within semiconductive material of the semiconductorsubstrate; forming trench isolation material within the isolation trenchand over the masking material outside of the trench effective tooverfill the isolation trench, the trench isolation material comprisinga silicon nitride-comprising layer having at least one material otherthan silicon nitride formed thereover; polishing the trench isolationmaterial at least to an outermost surface of the masking material; andetching said at least two of tungsten, titanium nitride and amorphouscarbon of the masking material from the substrate substantiallyselectively to the silicon nitride-comprising layer.
 9. The method ofclaim 8 wherein the masking material comprises amorphous carbon.
 10. Themethod of claim 1 wherein the etching is conducted selectively to all ofthe trench isolation material.
 11. The method of claim 1 wherein themasking material is void of silicon nitride.
 12. The method of claim 1wherein the masking material comprises titanium nitride.